In this entry in the long-running series of westerns, the Three Mesquiteers transform their ranch into a prison farm to provide a model for prison reform. They are opposed by a local contractor who wants to build a standard prison.

A heavy condensation of the 1936 serial Flash Gordon, with altered musical score. Flash Gordon, Dale Arden and Dr. Hans Zarkov visit the planet Mongo to thwart the evil schemes of Emperor Ming the Merciless, who has set his planet on a collision course with Earth. Released abroad as "Flash Gordon" for countries not interested in booking the serial, and never shown in the USA before 1950, where the title was changed to "Rocket Ship".

A bandit disguises himself as an officer in an attempt to woo a saloon singer.

Disaster seems imminent when scientists discover that the planet Mongo is about to crash into Earth. Luckily, heroic young Flash Gordon is on hand to lead an investigative mission into outer space and onto the speedily approaching planet. There, he and his best girl, Dale, who is along for the ride, learn that Ming, the devious ruler of Mongo, has purposely put the planet on a collision course with Earth, and only Flash can stop him.